Numerical investigation of the effect of thermal expansion coefficient and mushy zone constant on modelling of the phase change process to provide reliable selection criteria of modelling parameters

Document Type

Article

Publication Date

Summer 8-31-2023

Abstract

Phase change materials (PCMs) have been involved in many critical applications due to their ability to store thermal energy and stabilize the temperature. The accuracy of PCMs numerical modelling is affected by the software input assumptions including the thermal expansion coefficient and the mushy zone parameter. The thermal expansion coefficient is used to calculate the density value, to be applied in the modelling equations, but volume expansion is generally not considered by PCM modelling softwares. Due to this fact, the assumed value for the thermal expansion coefficient has to be selected properly, before conducting numerical tests. Another influential input is the mushy zone constant that has a significant effect on the output results, and it has to be selected from a wide range of values between 103 and 1010.

In this study a numerical investigation for the influence of both parameters was conducted to provide valid selection criteria. It was found that changing the expansion coefficient controlled the melting process time without affecting the melting profiles, where increasing the expansion coefficient accelerated the melting process, reducing the melting time and vice versa. The melting interface profiles were found directly related to the mushy zone parameter. Increasing the mushy zone parameter value decreased heat transfer rate through the mushy region, which significantly changed the melting profiles. These tests were repeated using different orientations to confirm these findings. Finally, reliable selection criteria were introduced to select the proper values for numerical modelling of phase change process. This selection process was tested using Lauric acid material at different orientations.

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